estimate 51.7 times 9
51.7 rouded would be 50 and 9 is closer to 10 so 50 times 10 is 500
51.7 -> 509 -> 10 (keep in mind that I'm rounding to the nearest 10 ok?) 50X 10----------- 00+ 500------------ 50051.7 x 9= 500 (estimated)
